Link adaptation technology is a technology produced for overcoming the time-variance of a wireless channel and utilizing the system resources effectively. A main advantage of the link adaptation technology is to improve the reliability of communications, the utilization rate of power resources and frequency, and the throughput of a system. The link adaptation in a LTE system mainly includes two manners which are adaptive modulation and coding (AMC) and power control. In the manners, the AMC refers to determining channel capacity according to condition of a channel, and dynamically adjusting a modulation and coding scheme according to the channel capacity, which can send information to the greatest extent, realize a higher data rate and improve frequency spectrum efficiency of a link, so as to increase the overall throughput of the system.
In the link adaptation technology used in a downlink direction, a modulation and coding scheme (MCS) is correspondingly found from a predefined a channel quality indicator (CQI) table based on a CQI fed back by a user equipment (UE). In order to save overhead of an uplink control channel, the CQI is fed back in combination with other uplink feedbacks, such as a precoding matrix indicator (PMI) and a rank indication (RI). The feedback can be divided into periodic feedback and non-periodic feedback in terms of time. The feedback may use a physical uplink control channel (PUCCH) or a physical uplink shared channel (PUSCH). The link adaptation technology used in an uplink direction directly determines a specific MCS based on an uplink channel quality measured by a base station.
Adaptive power control technology mainly adopts two universal uplink power control methods wherein the first one is to fully utilize residual power of a user, and improve signal quality of the user by increasing a transmit power, and an MCS with a higher order is preferably selected to maximize the throughput of a cell; and the second one is to control power density of a user received by a base station at a given level to restrain the interference of cells and improve the robustness of the signal environment of the cell and the performances of the whole network.
However, in the application of adaptive modulation and coding technology in the related art, in order to realize the link adaptation, a terminal is required to additionally measure a downlink channel quality (CQI) and report the measured downlink channel quality to a base station in uplink transmission, and the base station uses the CQI to find an MCS in a corresponding lookup table, which leads to a complicated flow, therefore and moreover, the terminal is required to measure an CQI additionally and specifically, so as to increase the overhead of the system.